Male courtship ultrasound produced by mesothoracic tymbal organs in the yellow peach moth Conogethes punctiferalis (Lepidoptera: Crambidae)

Abstract

Insect sound-producing apparatuses are mostly classified into two types: file–scraper and tymbal. Structures and locations of these organs are conserved in some phylogenetic groups, e.g., crickets, grasshoppers, and cicadas. However, moths have evolved diversified sound-producing organs, such as wing castanets and proboscis, in addition to the file–scraper and tymbal, in each species. Here we demonstrate that the yellow peach moth Conogethes punctiferalis (Guenee) (Lepidoptera: Crambidae) has developed mesothoracic tymbal organs never reported so far in insects. Tymbals are male specific and used for generating ultrasonic clicks in mating. We found eight to nine striae on the smooth surface of the tymbal membrane, suggesting the production of several clicks by a single buckle of the membrane in association with contraction/relaxation of the mesothoracic muscles. Acoustic data from click sequences support the idea that the series is generated by side-to-side asynchrony with an active/passive half cycle by an inward/outward buckle, and thus in click group (pulse) production, males emit 28 clicks with the right and left tymbals. The click-producing mechanism is similar, but not homologous, to those of other clicking species in five moth families. Thus, moths have acquired tymbal organs through independent and convergent evolution.